Xerographic printing is now very well known in the reproductive and printing industry. The evolution of laser printing systems has made the ubiquitous xerographic process an industry standard across a broad spectrum of product offerings featuring high speed, high quality and low cost performance. In most situations, the laser printer has replaced the typewriter in the office. This performance has, in turn, set a higher level of user expectations for quality, speed and performance in related printing applications. For example, in one industry, the airline industry, a great number of boarding passes and tickets are issued worldwide each day. These tickets, or coupons, are typically issued in multi-part format with the result that some copies are difficult, at best, to read. Also, in addition to being difficult to read, the multi-part forms either require carbon paper which is messy, or a special paper which is costly. The final product, in either event, is less than satisfactory. The airline ticket printing problem is but one illustration of printing problems occurring in point-of-sale situations.
One method of eliminating multi-part printing is to print all originals. This could only be possible if high speed, low cost printers were available to perform the printing function. When thinking of high speed printing, one naturally thinks in terms of laser printing systems. High-speed systems, however, appear to be optimized around complex mechanisms and relatively expensive light control techniques and do not seem suitable for low cost, low maintenance ticket sized printing. Low cost laser printer systems, on the other hand, are too slow, and the cost of consumables per printed page are relatively high.
In addition to the issues of printing speed and cost of operation, low-cost laser printers are subject to print quality related problems. For example, the laser printer creates the latent image on the drum by a scanning system which modulates the light source, and then focuses the modulated light pulses onto the drum via a series of lenses and rotating mirrors to create a raster line on the drum in the "fast-scan" direction. The modulated light, as it travels from the laser source to the drum, is subject to many influences, any number of which can cause the light beam and resulting printed image to be misregistered.
Misregistration can also result from slight changes in drum rotation speed resulting from motor surges or simply from varying motor loads. These misadjustments are known as "banding". It goes without saying that the quality of the final printing product is a direct function of the ability to control these types of misregistrations.
Another important aspect of high speed, high duty cycle printers, particularly when they are to be used at a critical point in a business process, such as at the airline ticket counter or airline gate, is their reliability. A corollary to reliability is that when trouble does occur, it must be repairable easily and inexpensively. In the modern, low-cost laser printer, this is accomplished, in part, by the concept of user-replaceable consumable elements. Typically, both the photoreceptor and the developer subsystem are user replaceable at frequent intervals. While this has the effect of maintaining good print quality performance, and lowering periodic service costs, the convenience of replacement cartridges, results in increased costs per printed page. Even with replacement cartridges, the useful life of low-cost laser printer systems is measured in terms of only several hundred thousand pages, because other parts of the print process wear out and are not readily user replaceable.
Thus, a need exists in the art for a printing system capable of high quality, high speed printing while allowing for low cost operation, maintenance and repair. In particular, there exists a need for a system for high volume commercial ticket printing applications where system lifetimes of several million coupons can be expected. To accomplish this, both the fuser assembly and the printer scanner system should also be easily user replaceable units.
A need also exists in the art for a high speed xerographic ticket printing system which accepts laser printing input commands but which neither contains the banding problems inherent with laser driven printing systems nor contains the difficulty of maintenance and adjustment inherent with such systems.